Global radio frequency interference in L-band SAR data from ALOS-1 and JERS-1 satellites

Abstract

Synthetic Aperture Radar (SAR) data acquisition is increasingly challenged by the overcrowded radio frequency bands, leading to the problem of Radio Frequency Interference (RFI), particularly at L-band. Knowledges about global RFI are important for the protection of the microwave bands allocated for active remote sensing, SAR system design and operation, as well as the systematic mitigation of RFI for SAR data end users. It is becoming more important as we are entering the unprecedented golden age of L-band SAR satellites. In this work, we develop algorithms, workflow and system for operationally measuring global RFI experienced by L-band SAR data. We define a data format for recording the RFI measurements, which facilitates the computation of a number of RFI metrics. We process all available L-band SAR data acquired by the JAXA ALOS-1 (2006–2011) and JERS-1 (1992–1998) satellites. For comparison with RFI in C-band data, we also process part of the ESA Envisat (2002−2012) data archive acquired in the same time frame (2005–2007). The final results provide a global view of RFI at L-band, showing its spatial and temporal variations. We find heavy RFI pollutions in East Asia, North America, and the region consisting of Europe, North Africa and the Middle East. Comparison of results from ALOS-1 and JERS-1 indicates the increasing trend of RFI pollution. Comparison with C-band Envisat result shows that RFI at L-band is significantly more severe than at C-band. Comparison of results from different polarizations shows that cross polarization data are more susceptible to RFI due to their lower radar backscatter. The global RFI distribution from L-band SAR data is found similar to that from L-band passive radiometers including SMOS and SMAP.